TY  - JOUR
A1  - Crumbach, Merian
A1  - Bachmann, Jonas
A1  - Fritze, Lars
A1  - Helbig, Andreas
A1  - Krummenacher, Ivo
A1  - Braunschweig, Holger
A1  - Helten, Holger
T1  - Dithiophene‐Fused Oxadiborepins and Azadiborepins: A New Class of Highly Fluorescent Heteroaromatics
JF  - Angewandte Chemie International Edition
N2  - Access to dithiophene‐fused oxadiborepins and the first azadiborepins attained via a modular synthesis route are presented. The new compounds emit intense blue light, some of which demonstrate fluorescence quantum yields close to unity. Cyclic voltammetry (CV) revealed electrochemically reversible one‐electron reduction processes. The weak aromatic character of the novel 1,2,7‐azadiborepin ring is demonstrated with in‐depth theoretical investigations using nucleus‐independent chemical shift (NICS) scans and anisotropy of the induced current density (ACID) calculations.
KW  - aromaticity
KW  - BN compounds
KW  - boron
KW  - isoelectronic analogues
KW  - polycycles
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-238996
VL  - 60
IS  - 17
SP  - 9290
EP  - 9295
ER  - 
TY  - JOUR
A1  - Hahn, Lukas
A1  - Luxenhofer, Robert
A1  - Helten, Holger
A1  - Forster, Stefan
A1  - Fritze, Lars
A1  - Polzin, Lando
A1  - Keßler, Larissa
T1  - ABA Type Amphiphiles with Poly(2-benzhydryl-2-oxazine) Moieties: Synthesis, Characterization and Inverse Thermogelation
JF  - Macromolecular Chemistry and Physics
N2  - Thermoresponsive polymers are frequently involved in the development of materials for various applications. Here, polymers containing poly(2- benzhydryl-2-oxazine) (pBhOzi) repeating units are described for the first time. The homopolymer pBhOzi and an ABA type amphiphile comprising two flanking hydrophilic A blocks of poly(2-methyl-2-oxazoline) (pMeOx) and the hydrophobic aromatic pBhOzi central B block (pMeOx-b-pBhOzi-b-pMeOx) are synthesized and the latter is shown to exhibit inverse thermogelling properties at concentrations of 20 wt.% in water. This behavior stands in contrast to a homologue ABA amphiphile consisting of a central poly(2-benzhydryl-2-oxazoline) block (pMeOx-b-pBhOx-b-pMeOx). No inverse thermogelling is observed with this polymer even at 25 wt.%. For 25 wt.% pMeOx-b-pBhOzi-b-pMeOx, a surprisingly high storage modulus of ≈22 kPa and high values for the yield and flow points of 480 Pa and 1.3 kPa are obtained. Exceeding the yield point, pronounced shear thinning is observed. Interestingly, only little difference between self-assemblies of pMeOx-b-pBhOzi-b-pMeOx and pMeOx-b-pBhOx-b-pMeOx is observed by dynamic light scattering while transmission electron microscopy images suggest that the micelles of pMeOx-b-pBhOzi-b-pMeOx interact through their hydrophilic coronas, which is probably decisive for the gel formation. Overall, this study introduces new building blocks for poly(2-oxazoline) and poly(2-oxazine)-based self-assemblies, but additional studies will be needed to unravel the exact mechanism.
KW  - inverse thermogels
KW  - physical hydrogels
KW  - poly(2-oxazine)
KW  - poly(2- oxazoline)
KW  - self-assembly
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-265124
VL  - 222
IS  - 17
ER  -